Polishing pad window

Abstract

The polishing pad is suitable for polishing or planarizing at least one of semiconductor, optical and magnetic substrates. The polishing pad has a polishing surface, an opening through the polishing pad and a transparent window within the opening in the polishing pad. The transparent window has a concave surface with a depth that increases with use of the polishing pad. A signal region slopes downward into the central region for facilitating debris removal and a debris drainage groove extending through the central region into the polishing pad. Rotating the polishing pad with polishing fluid in the debris drainage groove sends debris from the central region into the polishing pad through the debris drainage groove.

The invention claimed is: 
     
       1. A polishing pad suitable for polishing or planarizing at least one of semiconductor, optical and magnetic substrates, the polishing pad having a polishing surface, an opening through the polishing pad, a radius that extends from a center of the polishing pad to a perimeter of the polishing pad and a transparent window within the opening in the polishing pad, the transparent window being secured to the polishing pad and transparent to at least one of magnetic and optical signals, the transparent window having a concave surface with respect to the polishing surface, the concave surface having a maximum depth in a central region of the transparent window as measured from a plane of the polishing surface that increases with use of the polishing pad; a signal region in the transparent window adjacent the central region and on a side closest to the center of the polishing pad for transmitting at least one of optical and or magnetic signals to a wafer, the signal region sloping downward into the central region for facilitating debris removal and a debris drainage groove extending through the central region into the polishing pad wherein rotating the polishing pad with polishing fluid in the debris drainage groove sends debris from the central region into the polishing pad through the debris drainage groove and wherein the depth of the debris drainage groove is greater than the depth of the central region. 
     
     
       2. The polishing pad of  claim 1  wherein the debris drainage groove extends along the radius from the center of the polishing pad to the perimeter of the polishing pad. 
     
     
       3. The polishing pad of  claim 1  wherein the debris drainage groove extends through a circumference of the polishing pad. 
     
     
       4. The polishing pad of  claim 1  wherein the window is an optically transparent polymer. 
     
     
       5. The polishing pad of  claim 1  wherein the polishing pad is porous, the transparent window is non-porous and casting of the polishing pad around the transparent window secures the transparent window to the polishing pad. 
     
     
       6. A polishing pad suitable for polishing or planarizing at least one of semiconductor, optical and magnetic substrates, the polishing pad containing fluid-filled microspheres and having a polishing surface, an opening through the polishing pad, a radius that extends from a center of the polishing pad to a perimeter of the polishing pad and a transparent window within the opening in the polishing pad, the transparent window being secured to the polishing pad with a lateral spacing less than an average diameter of the fluid-filled microspheres and transparent to at least one of magnetic and optical signals, the transparent window having a concave surface with respect to the polishing surface, the concave surface having a maximum depth in a central region of the transparent window as measured from a plane of the polishing surface that increases with use of the polishing pad; a signal region in the transparent window adjacent the central region and on a side closest to the center of the polishing pad for transmitting at least one of optical and or magnetic signals to a wafer, the signal region sloping downward into the central region for facilitating debris removal and a debris drainage groove extending through the central region into the polishing pad wherein rotating the polishing pad with polishing fluid in the debris drainage groove sends debris from the central region into the polishing pad through the debris drainage groove and wherein the depth of the debris drainage groove is greater than the depth of the central region. 
     
     
       7. The polishing pad of  claim 6  wherein the debris drainage groove extends along the radius from the center of the polishing pad to the perimeter of the polishing pad. 
     
     
       8. The polishing pad of  claim 6  wherein the debris drainage groove extends through a circumference of the polishing pad. 
     
     
       9. The polishing pad of  claim 6  wherein the window is an optically transparent polymer. 
     
     
       10. The polishing pad of  claim 6  wherein the polishing pad is porous, the transparent window is non-porous and casting of the polishing pad around the transparent window secures the transparent window to the polishing pad.